Electric gaseous discharge device



Aug. 12, 1952 J. A. RoY ET Al.

ELECTRIC GASEOUS DISCHARGE DEVICE Filed NOV. 8, 1947 vu. Dm R U H .I R H P rr. s U IU. a.

INVENTORS ATTGRNEY *put throughout -nits life. i 'course of their lives,l electric; gaseous discharge l5,` .Ilflh $35,@

ing the brightness or 680,527-, nieu-June 29,-;1

Patented Aug. 12, 1952 UN ITED ES .Y rf 1 1 immuni;

npncrmo GAsEoUs nrs-2 Y Joseph Arthur Roy, Danvers;1

Topseld, Mass., assignorsifto S-yl f Products Inc., Salem v Massachusetts Mas a Application November s, 1947, seminal.

' u 2 Claims.

1 This invention relates to electricwgaseous dis- .A charge devices and more particularly'to a lmeans for-,improving the maintenance .of .thegradiant .flux output ofsaid devices durinaliief- In the manufacture of: electric;` gaseous dis- 5 byproyding thcinner p vall of thezvlalp charge devices, suchas `iiuorescent lamps. and germicidal lamps, for example, one of the primary objects is to make a; device which will be characterized by a highfradiant4 flux output throughd'fwth.;bii @igt-emis- .The lumen maintenance fand Vthe vlorightness durv .ing lifeof flucrescentllamps mayalsobe mqreased with. e Surface.contamina@marini-Orl. of its compounds before the luores" i v.is appliedtherctogli es nged, lt 0n. orits 5 oxides niaybe added the, ravv m erial fmixture out its life. In the 'case of devices emitting vislo 0f soniegfluorescent-materialsghefor they arcred ible light, the radiant ilux is usually expressed in -terms of lumens per'watt. The ideal device would be one which suieredno loss infradiant 'out- However, during the devices suler a loss'in'tlieir radianti flux" output. In 'some cases the lossV 'is' greater thaninfothe'rs. In some cases a substantial loss is suffered early inli'fe and the loss increasesas the'lifeiexpectancy of the device is approached.- -An object vof this-inventionis to provide means for reducing the lcssin radiant `iluxfoutput during the life o f electric gaseous discharge-devices. AVAnother'olojecti's to providegmeansforfincreasu I,

lumens-per yyatt output `of-acvenvelope. 'I h e lamp. envel e iluo'rescentl lamp duringlifesjdjvIn our-` co`pendin`g `japplication;Y SeriahNo. nowA abandoned,l of which thisl 'application' is `a continuation in part we pointed 'outf 'that fthefjafiditihii ofj'fsmallzsgo the gaseous discharge .device is quitejsmall. For

quantities of Sb'zOa to a suspensionof luminescent material adapted to be used as a coating foriiuorescent material adapted to be used as a coating for uorescent lamps aidsconsiderably in mainexample, in the case'. of ,Iffluorescent lamps, the L.,P. W. maintenance and thevbrightness during life, is' improved when thelquantity of antimony or fits compoundjwhich is vadded during manufacture taining a high L. P. W. output throughout the l35' vis, greater thangOOS %v and less 'than 1%-1 jThe life of thelamp. We also indicated that this addition of SbzOs to the luminescent material suspension vwas particularly satisfactory. when zinc silicate', zinc beryllium silicate,A and/or magused. I

inthe form` of the free metalor certain -o'fitsfcompounds, suchffasthe oxides4 for' exampll -is`- beneaddition ofjmore than 1% tends 'to depress the 'brightness of the lamp early inlifev andffro'm a Q practical Vvcommerciali:vewpointfthis `is not -desiable..- When theiamount ofjantimony 'or al com- 'nesium tungstate was the luminescent materialf140 4'pound,thereof'which.is adddiskeptlbelow 011%,

eial not only to fluorescentlampsbut to-other"f45 0.1% tends to' cause seriousidis'`coloratio1inear the v types of electric gaseous dischaiig device'sypa'rticularly when the envelope is 'a'.I soda-'lime or horosilicate glass. The elect on themaintenance of the radiant ux outputof these devicesis parends of the lam'p envelope and,- inthe absence of some means for correcting this condition', "the ..lam'ou'nt oi.. 'antimony or, a compound i thereof ,@whichus adde'dshould' notbe more' than';0. 1%.

ticularly beneficial when the devicesgcontain a" 50,' With reslpect l' to discoloration "thereforeffthe metal vapor, such as mercury. ,i .j

Inthecase of fluorescent ilamps, the envelope A of which Vis usually; soda-lime glass, 'antimpny may beadded-to the iinishedphosphonnot nonly amount of antii'nfony- 'or' a "co und. thereof ...which 'added is', critical.' `'The preferred'additi on, .in Viewy of these sevt-lralf'factors'y is.. about in the f orm :of v,the trioxidfbutthe free meta, 55. Figure; 1'sfas12ije-feietti'ofai meegaan' i a '.by suspending it in a suitable lacquer and causlng it to flow over the Wall of the lamp envelope. After this suspension has dried, the lamp envelope is heated in an oxidizing atmosphere at a temperature high enough to burn oi the lacquer,

such as between about 450 C. to about 550 C.'

Stems 3 are sealed in the ends of Ythe envelope. Lead wires 4 are sealed in the stems and 'the inner ends thereof serve as supports for lamentary electrodes 5 which are provided with 'a coating of an electron emissive material, such as the alkaline earth oxides, for example, as shown ln the Lowry Patent 2,258,158. Thelamp en velope is then exhausted and provided with a fllling of an inert gas, such as argon, at low pressure, of the order of .ar-few millimeters, such as three millimeters for example.- A small quantity of mercury Gis also disposed within the envelope. During exhaust, the lamp is heated at a temperature below-that at which the lamp envelope is 'baked toburn offtheflacqur. The lamp is usually operatedat a 'mercury vaporpressure of between 1 to 20'microns. Y

Several 'of the examples below indicate the beneficial effect whichthe Y'addition of a small quantity ofantimony or certain-oi its compounds toa flnished phosphor beiore'it ls applied te the wall o f the lamp -`envelope has on theI L. P. W. maintenance and the Ybrightness during life of fluorescent lamps. -In -these examples, -the antlmny or a compound thereof ,-for convenience,

` has been added'directlytothe suspension of fluorescentxnaterial with whichv the lamp envelope is coated. -Howeven the antimony or a compound th'ereoi maybe mixed with the powdered ilnlshed phosphor before it is put in suspension, or lt mayv be mixedin a suitable medium Yand this'mixture added `to 'the l suspension w'itl'lout departing from thesplrit of. the invention. The suspension flthe finished phosphorand antinlony or a compound 'thereof shouldbe milled to insure thorough ldis-V persian` of the yantixrioriy or'the compound used. This willfgi've the antimony aparticlevsizeabout the same as that Yof the finishedphosphor.

EXAMPLE :L -ZINC BERYLLIUM MANGANESE y if SILICATE The Vzinc beryllium` manganese silicate may be prepared by mixing about 585 "gramsof ZnO,

about 20 grams of BeO,about 56 Vg'ram's'of an activator, MnCOa, about S-grams of Vsilicio acid (containing about 277 grams of SiOz) and 0.6

. grams of a iiuxingA agent,fZnF2. This mixture is fired at about v2230" 170,226()lo F. for from 4 to 6 hours to give a :particle Siae of .about 2.0 to' 2.5

microns. The red material is then ballmilled,

and suspended in a suitable lacquer such as nitrocellulose and the viscosity thereof may beradjust'ed by the addition .fof a solvent such' as' amyl acetate or butylacetate. .A small quantity of a yr'ilasticiz'er such as di-{methylmhthalate vmay also' be added. Y t

To this suspension a small 'quantity of powdered SbzOs ls added. i The SbzOs maybe milled witha small amount of the same lacquer in which the luminescent material is suspended and thenfmxed with the luminescentmaterial suspension or it may be added directly. In'weither casa-the suspension of luminescent material with the SM05 added should be milled to insure thorough dispel'- sion. This suspension is then applied to* theelamp i LMENs PEP. WATT Hrs. Hrs. Hrs. Hrs. Hrs. Hrs

0% SblO; 61.0 54.8 51.4 49. 6 47. 2 45. B l5% SbgO; 63.6 58.0 55. 4 54 0 5l. 8 49. 8 30% SbgOs 58. 4 55. 2 53. 4 52. 2 50. 4 48. 8

-Thus it may be seen fromthe above tabular data that the addition ofV SbzOs to the suspension of luminescent material effects-a substantial -decrease in the rate of -loss of lumens-per-watt output and an increase in the brightness ofdauorescent lamp during its life. l

EXAMPLE 11.-zINo BERYLLIUM i MANGA- NEsE SILICATE ln this test the same raw materials .in substantially the same proportions were used, except that about .08% Pho and about .001% snotty weight of the `zinc oxide were added to `the-raw material mixture. The additionv of small quantitiesof lead and arsenic to the raw materials used in making luminescent zinc silicates .usually enhances the L. P. W. maintenanceand brightness of fluorescent lamps. The mixture of raw materials was `fired for from 3 `to dliours at about 2210J F., ball-milled,-A and 'then' iired again for about the same time and at about the same temperature. Theparticle size of the iinished phosphor Was-about 3.75microns. The sus- LUMENs PEB. WA'H `This test indicates Vthatna still furthergimprovement in lumen 'maintenance and'` brightness can be, obtained, in addition to -that obtained by the addition of lead and'arsenicto the 'raw `material mixture, by the-addition of a small amount ofSbzOato the -iinished phosphor. 1

the following tables:

:about .05% sbzoa by weight of .the.finished` phosphor -Was added thereto.

The eiect whichfthe addition of SbzOs had on the lumen maintenance and the brightness of 40 watt lamps coated with this suspension is indicated n the follow- .ing table:

' LUMENs PEB. WA'i'r 4 0 :100' `500 1 Hrs. Hrs. Hrs.

Shao: 51.2 47.2 42.6 05% 8h10, 50.6 48.0 44.4

Thus `it may be seen that the addition of .05% SbzOa to a suspension of magnesium tungstate enhances the lumen maintenance and the brightness ofthe fluorescentgilamp.

EXAMPLE Iva-BARIUMy LEAD sILICATE 'In this test a mixture of about 1 Vmol of -BaCO3,

about 1.62 mois of SiOz and about 0.12 molof an activator, PbCos, was ball-milled in-water, dried,`

crushed and red for about 2 to 6 hours-at about 51850 F. The suspensionof this iired material Was prepared in substantially the same way as the suspension in Example I and-'about .05% SbzOs by weight of the finished phosphor was added thereto. The eiect which the addition of SbzOa had on the lumen maintenance of Watt lamps coated with this suspension is indicated in LUMENS PER iWATT 0 100 300 5001 900 Hrs. Hrs. Hrs. Hrs. Hrs.

0%sb1o. 20.5 '10.6' 15.5' 15.0' 13.5 .0521.66.03 19.8 11.6565 16.8 14.9

' j Thus it may be 'seen that't'he addition of the Sb203 to a suspension of barium silicate decreases the rate of loss in'lumenmaintenance and increases the brightness during the life of the lamp.

- EXAMPLE v cALCIUM LEAD `M'AISIGA'liIEsE r sILJcATE-MAGNESIUM TUNGsTATE l BLEND Tests were run on various blends of calcium lead manganese silicate and magnesium tungstate 'which are used to give white and daylight fluoy rescent lamps. The calcium lead silicate component was prepared by mixing about 1 mol of CaCOa, about 1.2 mols of SiO2, about 0.066 mol of ff an' activator, MnCOa and aboutl 0.0035 mol of "PbFz, which in this case serves as an activator and a fluxing agent. This mixture was ballmilled in water,A dried,V crushed and red for about 6 hrs. at about 1900o F. and again for about 6 hours at about 2100 F. This component was then mixed in the'desired proportion with magnesium tungstate which was prepared substantially; as indicated above in Example III. Three tests were run. one with a daylight blend and two with a white blend. In the daylight -test and in one of the white tests, .05% antimony in the forni of the free metal was added to the suspension in some'cases, and in other cases .05%

' 'Sb2O3 was added,` both of these-percentages being 'by'weight offthe finished phosphor' Forty watt lamps were employed vin these tests.

- made therefrom..

J'These tests indicate that the addition'ofantimony, either in the form of the free metal or the trioxide, tothe suspension of va blend of magnesium tungstate andcalciumlead manganese silicate enhances thelumenmaintenancel-and the brightness of the lamps. y v

VI Z1I\TC BERYLLIUM MANGA- NESE smrcATE-MAGNESIUM TUNGSTATE -These two materials were Ipreparee'i'in substantially the same manner and the several-.ingredients thereof Vwere present in substantially the same proportions as indicated` in' Examples Land III above, and the -r'ed' powders `were then blended in proportions tov give a white lamp." S

rIn T'est 'Iv below,V various amounts" off SbzOa lwere added to thefsuspensionof' thisblend-and 40 Watt uorescent lamps were made.

LUMENs PER WATT 0 115 812 529 852 Test): Hrs. Hrs. Hrs. Hrs. 'Hrs This test indicates that,'even when amounts as small as .005% are added,` the lumen' maintenance and the brightness is improved.

I I rest II.

. In this test the blend was substantially the same except that the zinc beryllium magnese silicate was prepared as in Example l1 above. Variousamounts of SbzOs vbased on the weight of the nished phosphor were added to the suspension of this blend and 40 Watt lamps were LUMENs PER WATT Hrs. Hrs. Hrs. Hrs. Hrs. Hrs. Hrs

60.0 56.8 55.0 52.8 51.2 47.8 46.2 59. 4 58. 4 57. 6 56.0 55. 4- 52. 8 61. O 59. 2 58. 4v 58.0 56. 2 55. 6 52. 6' 51.4 58. 8 58. 2 57. 6 55. (iV 55.0 53. 2 52. 0

This test indicates that as much a's .3% SbzOa caribe employed with benecial results both on the lumen maintenance and on thebrightness during life. f y

as; that describedA in Example III above.

E7 Test m VThe results of this test indicate that Athe ad-l dition of various small amounts of 'antimony .metal to the iluorescent .material suspension has a beneficial eiect on lumen maintenance corn- -parable -to the advantages obtained ibfy adding 51u03. l i

'VII-VARIOUS ANTIMONY COM- POUNDS ADDEDTO BLEND OFYZINC BE'- RYILIUM MANGANESE V`SIlJILJIlE" AND MAGNESIUM TUNGSTAIE f lIn this test various antimony compounds were added to a suspension vof vzine beryllium manganese silicate-magnesium tungstate blend and 40 watt White lamps were made. The zine beryllium manganese silicate was substantially the same as that described in Example 1I above, and the magnesium tungstate was substantially the same The quantity of the antimony compound in each case was based on the Weight of the nished phosphor. The following results were obtained:

' VLUMENS 'PER WATT Hrs Hrs. Hrs.

Control 64.0 57. 0 55.0 SbzOa 63. 2 60. 8 59. 2 05% Sb z 63. 0 60. 8 59. 4 1% Shi 61:5 59. 2 58.0 05% SblOx 64:8 460. 8 59. 4 SbzOi 64..'8 59. 6 58. 2 05% KSbClHlOf-. 64. 8 59. 2 58. 0 .1% KSbC4H4O 64. 2 G0. 2 59. 2 05% SbSe- 65. 0 59. 56. 6 .1% SbSe..r.- 64.0V 59.8 58. 4

The results of this test indicate that several antimony compounds other than the oxides have v Va beneficial eiect onthe lumen maintenance and the brightness of fluorescent Iampsalthough any antimony compounds which react chemically With the fluorescent material .should generally be avoided.

In all 'of the examples above, :antimony or one of its compounds was addedto the finished phosphor. However, as pointed out above, in the case of some fluorescent materials, the antimony or its compounds may be added to the unred raw material mixture .With-beneficial results on the Vlumen maintenance.

EXAMPLE VII- ANTIMONY OEIIDEIS TO ZINC BERYLLIUM MANGANESE 'SILI- CATE UN FIRED RAW MATERIAL MDiTURE In this test the -zinc beryllium silicate was of the same type ang-i'lwas prepared in substantially the same mannen-.as thatof Example I- above, except that various amounts of SbzOa and In Athis test the same 'fluorescent material gnge' T1115 *est was maderwl'th '20 "Watt `blend was used Yas used in Test II immediately p L n "P v above. In this case, however, various amounts UMEM vER I ATT p y of the free metal were added to the suspension 5 o 162 315 911 .based on the Weight of the finished phosphor, Hrs Hrs Hrs Hm with4 the following results:

LUMENs PER WATT 38.7 35.0 A '45.3 42.0 si ss o os 31s 49s 87s "nrs nrs. nrs. nfs. Hfs. 1B-3 451 'No antimony 64.4 '68.6 56.4y 165.0 63.2 This test.- indicates that when various Yamounts Y 32 61' 59:0 .5s-3 56'0 of 4an oxide of antimony are added to the un- .e 62.4 59.2 68.9 56.2 .i0 .2 60.8 saz l58.6 56.8 fired raw material mlxture, the lumen mainte- 323 ggf 222 nance andthe brightness are beneficiallyafeoted. s m-AN'r-'IMONY vraioxmn AD- DITION TO 'TUNGSTATE AUN- FIRED RAW MATERIAL lMlXTUlBE Example II-I above-shows that the addition of SbzOa to the coating suspension of magnesium tungstate improved the lumen maintenance and brightness. However, the -reverse is true when SbzOs is added to--the-unfired raw material mixture. Even a very small. amount of SbzOs .introduoed at'this point seriously reduces the'lumen maintenance and brightness as shown in the following table: y

- LUMEiNs PER WATT The amount of antimony is expressed in percent of tungstije oxide (W03).

The eect of adding SbzOs to the unred raw material mixture of magnesium tungstate is thus opposite tothe effect` obtained by adding vSbzOa to the unredvrawmaterial mixture of zinoberyl- .liuin manganese silicate (Example VIII above) -lX-ADDITION OF ANTIMONY OXIDES TO ZINC BERYLLIUM MANGA- NESE SILIICATE UNFIRED RAW MATERIAL MIXTURE AND TO FINISHED PHOSPHOR -LUMENS PER WATT o 16o lsoif-:6to seo 'Test I vHrs.v Hrs.: Hrs. rs.` Hrs.

vIest 51.33 19.0 415.7u 47.2 4&6 VControl 50.0 46.9 44.0 41.7 .a

fin Test 11,?.65-72, 'ships was .added tonie raw =material mixtureand 05% SbzOs was added to the inished phosphor fini-the 'case of the test lamps, Whereas the control lamps had .05% SbzOs added to the raw material mixture only.

Thus these two tests indicate that when a small amount of an oxide of antimony is added to a finished phosphor which [already contains a small amount of an oxide antimony, a further gain in L. P. W. maintenance is obtained.

In all of the above examples and tests, the envelope of the fluorescent lamps was a soda-lime glass. As pointed out above, the addition of antimony or certain compounds thereof is beneficial not only on lthe maintenance of the radiant flux output and brightness during life of liuorescent lamps but on other electric Igaseous discharge devices, which contain a small quantity of `a metal vapor such as mercury. The addition of antimony or certain compounds thereof to a germicidal lamp improves the maintenance of the radiant flux output thereof tremendously. The germicidal lamps on which the tests below were made was substantially the same as the lamp shown in Figure 1, except that the lamp envelope was a borosilica'te glass substantially free of iron and designed to transmit germicidal ultra-violet radiations and the lamp envelope did not have a fluorescent coating thereon. Since `germicidal lamps are used extensively in refrigerators, Test I below Was made -at 32 F. Test II Was made at 80 F. In each test, the lamp envelope was coated with a mixture of 0.05 gram SbzOa per c. c. of a lacquer such as nitrocellulose, and the envelope was heated t burn olf the lacquer. The lamp was then processed in the conventional manner. The measurement of the radiant flux output in the tables below is in arbitrary relative units.

EXANIPLE XI.-GERMICIDAL LAMPS `Thus by providing the borosilicate glass envelope of a germicidal lamp with a surface high in SbzOa content the maintenance of the radiant ux output of the lamp is enhanced considerably, regardless of the ambient temperature conditions under which the lamp is operated.

In the several examples above, we have shown that the addition of a small quantity of antimony in the form of the free metal or certain of its compounds, enhances the maintenance of the radiant flux output of electric gaseous discharge devices. We have indicated various methods which may be employed in introducing the antimony or its compounds into the discharge devices. In the case of fluorescent lamps, when the -antimony or its compounds is added to the 10 finished phosphor, to the suspension thereof, for example, We have indicated in each case, the quantity of the antimony or its compound which is added at this point. As was pointed out above,

after the lamp envelope is coated, the envelope i is heated to a temperature of about 450 C. to about 550 C. Analyses of the fluorescent coating in .the finished lamp indicate that some of the antimony or its compound which was added to the nished phosphor is lost, probably due to the baking. For example, when about .05% of an oxide of antimony based on the Weight of the finished phosphor is added thereto, only about .015 of antimony is left in the fluorescent coating in the finished lamp. When between .005% to 031% of an oxide of antimony is added to the finished phosphor, the .amount of antimony which is left in the fluorescent coating in the finished lamp is between about .0015% to about .03%.

Unlike some other metals or oxides, antimony oxides in the amounts used herein do not appear to aifect the coating adherence, neither increasing nor decreasing it. When antimony met-al is added to the suspension, it is probably oxidized, at least in part, during the bak-ingv process.

Putting the antimony in the nal phosphor suspension appears to be helpful With all fluorescent materials, excepting possibly those with which it might chemically react, and can therefore be used even with those phosphors which it adversely aifects if used in the unflred raw material mix. The beneficial action of the antimony 1l. A fluorescent lamp comprising a glass en- V velope, electrodes .sealed in said envelope, a filling of at least one inert gas at low pressure in said envelope, a quantity of mercury in said envelope, and a coating on the inside Wall of said envelope, said coating comprising .an activated fluorescent ifnaterial and about 0.015% antimony in the oxide crm.

`2. A fluorescent lamp comprising a glass envelope, electrodes sealed in said envelope, a filling of at least one inert gas at low pressure in said envelope, Ia quantity of mercury in said envelope, and a coating on Ithe inside wall of said envelope. said coating comprising an activated fluorescent material and between about 0.0015% to about 0.03% antimony in the oxide form.

JOSEPH ARTHUR ROY.

ROBERT S. IVES.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number Name Date 2,177,691 Dawihl Oct. `351, 1939 l2,241,950 Huniger May 1'3, `1941 2,306,626 Huniger Dec.' 29, 1942 l2,316,366 Ruttenauer Apr. 13, 1943 2,317,977 Casellini May 4, 1943 2,344,081 Claude Mar. 14, 1944 2,433,404 Smith Dec. 30, 1947 FOREIGN PATENTS Number Country Date 578,195 Great Britain June 19, 1946 OTHER REFERENCES Websters New International Dictionary (2nd ed.) 1934, pg. 1062, Merriam-Webster, Springfield, Mass. 

1. A FLUORESCENT LAMP COMPRISING A GLASS ENVELOPE ELECTRODES SEALED IN SAID ENVELOPE, A FILLING OF AT LEAST ONE INERT GAS AT LOW PRESSURE IN SAID ENVELOPE, A QUANTITY OF MERCURY IN SAID ENVELOPE, AND A COATING ON THE INSIDE WALL OF SAID ENVELOPE, SAID COATING COMPRISING AN ACTIVATED FLUORESCENT 